Methionine, which can be produced by chemical and biological synthesis, is used as a raw material for the synthesis of infusions and medicines as well as for the synthesis of feed and food additives. Recently, a two-step process for producing L-methionine from an L-methionine precursor, produced via fermentation, by an enzyme conversion reaction was disclosed (International Patent Publication No. WO 2008/013432). International Patent Publication No. WO 2008/013432 discloses that O-succinylhomoserine and O-acetylhomoserine can be used as a methionine precursor in the two-step process, and it is very important to produce methionine precursors in high yield for economical large-scale production of methionine.
LeuE is known as a leucine export protein. As one of the proteins belonging to homoserine/homoserine lactone efflux protein (RhtB) family, LeuE is a protein present in the inner membrane and is known to have the role of exporting leucine and its analogues as a putative uncharacterized transport protein.
In the prior art relating to LeuE, it is known that a purine nucleoside or purine nucleotide can be produced by enhancing an amino acid sequence of leuE (yeaS) gene or a modified amino acid sequence thereof, and the amount of amino acid production can be improved. Additionally, a modified leuE having the activity of exporting cysteine is known.